Silver halide emulsion stabilized with a bidentate heterocyclic compound containing a sulpho or a carboxyl group

ABSTRACT

Photographic materials comprising a light-sensitive silver halide emulsion and containing a stabilizer against formation and growth of fog are described. The stabilizer is a bidentate heterocyclic compound having at least two nitrogen coordinating atoms for silver and a water-solubilizing carboxyl or sulphogroup. Fog growth is prevented without inhibiting emulsion sensitivity.

United States Patent [191 Willems et al.

[ 1 SILVER I-IALIDE EMULSION STABILIZED WITH A BIDENTATE HETEROCYCLIC COMPOUND CONTAINING A SULPI-IO OR A CARBOXYL GROUP [75] Inventors: Jozef Frans Willems, Wilrijk; Frans Clement Heugebaert, Kontich; Robert Joseph Pollet, Berchem, all

of Belgium [73] Assignee: AGFA-Gevaert N.V., Mortsel,

Belgium [22] Filed: May 10, 1971 [21] Appl. No.: 141,995

Related US. Application Data [63] Continuation-in-part of Ser. No. 795,077, Jan. 29,

1969, abandoned.

[30] Foreign Application Priority Data Feb. 22, 1968 Great Britain 8653/68 [52] US. Cl. 96/76 R, 96/109 [51] Int. Cl G036 1/34, G036: 1/48 Apr. 30, 1974 [58] Field of Search 96/109, 76 R [56] References Cited UNITED STATES PATENTS 3,137,578 6/1964 De Selms 96/109 3,305,362 2/1967 Riester et al 3,042,521 7/1962 Deysch et a1. 96/109 X Primary Examiner-.l. Travis Brown Assistant Examiner-Won H. Lovie, Jr.

Attorney, Agent, or Firm-A. W. Breiner ABSTRACT BIDENTATE I-IETEROCYCLIC COMPOUND CONTAINING A SULPHO OR A CARBOXYL GROUP The present application is a continuation-in-part of Application Ser. No. 795,077 filed Jan. 29, 1969 now abandoned.

This invention relates to improved photographic materials comprising light-sensitive silver halide emulsions and more particularly to photographic materials having less tendency to fog formation while still possessing the same light-sensitivity.

It is well known that light-sensitive silver halide materials comprising gelatin silver halide emulsion layers are subject to fogging. Fogging in general and chemical fogging in particular may be defined as the formation of a uniform deposit of silver on development which is dependent on a whole series of circumstances and factors namely on the nature of the emulsions, on their age, on the conditions under which they have been stored, on the development conditions, etc. For particular development conditions the fog tends to be greater as the time of storage and the temperature and relative humidity of the atmosphere in which the emulsions are stored are increased. Consequently it is known to carry out accelerated tests called incubation tests on the stability of photographic emulsions by storing them at elevated temperature and humidity and then determining their sensitometric characteristics.

Addenda to the photographic material known as stabilizers or antifoggants protect the light-sensitive silver halide emulsions against formation and growth of fog particularly in highly sensitive emulsions and in emulsions which are to be stored under conditions of high temperature and humidity as is for instance the case in tropical countries.

It is well known to use compounds of the triazolopyrimidine type (azaindolizines) as stabilizers for light-sensitive photographic silver halide emulsions; Although these compounds are very effective stabilizers, emulsions containing them still show a tendency to fog formation in extreme storage circumstances i.e. at very high temperatures and humidities and in extreme development circumstances e.g. rapid processing at elevated temperatures.

It is also known from vU.S. Patent specification No. 3,137,578 to protect light-sensitive silver halide emulsions against the growth of chemical fog during storage by addition of benzimidazoles substituted in the 2- position by a Z-pyrrolylgroup, a 2-furylgroup, a 2- thienylgroup, a 2-pyranyl group, a 2-thiopyranyl group, a Z-tetrahydropyranylgroup, a Z-tetrahydrofuryl group, a Z-tetrahydrothiopyranyl group and the like heterocyclic groups.

These compounds, however, have but a very low foginhibiting effect and reduce the emulsion sensitivity markedly.

It has now been found that heterocyclic bidentate reagents for silver comprising at least one watersolubilizing group and more particularly compounds s r sp nsl nstq s fqllqw yass s a qrr r ar wherein: 7* "W R stands for hydrogen or lower alkyl comprising at most four carbon atoms including substituted lower alkyl,

Z represents the atoms necessary to complete a heterocycle including a substituted heterocycle and a heterocycle with fused ring e.g. imidazole, benzimidazole, naphthimidazole, imidazopyridine, imidazoline, pyrazole, triazole, tetrazole, etc.

A stands fora chemical bond, alkylene such as methylene, ethylene, tetramethylene etc. including alkylene interrupted by oxygen or a -N(R) group wherein R has the same significance as above, my]- ene, alkenylene, such as vinylene and -S-alkylen-S- or S-alkylenethe alkylene groups of which can be interrupted by oxygen or ,a N(R)- group wherein R has the same significance as above,

X stands for a heterocycle including a substituted heterocycle and a heterocycle with fused ring, said heterocycle comprising the moiety =N, for example imidazole, benzimidazole, naphthimidazole, imidazopyridine, imidazoline, pyrazole, pyridine,

I v quinoline, thiazole te trazole, triazole, etc a n d wherein a water-solubilizing group, more particularly .a COOM or -SO M group with M hydrogen, ammonium, a metal atom, an organic amine, etc., is linked directly or indirectly to the grouping Z and/or X and/or A, are particularly good stabilizers and antifoggants for photographic light-sensitive silver halide emulsions without causing an objectionable desensitization of the light-sensitive material.

Moreover, it has been found that the compounds according to the invention are very suitable for use in combination with stabilizers of the triazolopyrimidine type, particularly in extreme storage and development circumstances in order to reduce the fogging tendency of the light-sensitive emulsion without giving rise to an appreciable desensitization thereof.

The compounds corresponding to the above general formula are referred to as being bidentate heterocyclic compounds which means that they are bidentate ligands for forming complexes with silver i.e.'they should contain at least two coordinating atoms for silver, the n tr s r m, 09119.-..

N .lr. group of the heterocycle being one of the coordinating atoms and the nitrogen atom of the =N moiety in X being the other coordinating atom. Thus, the moiety =N in X is an essential feature of the compounds of the invention.

The presence of (a) water-solubilizing group(s) is also an essential feature of the compounds of the invention since compounds corresponding to the above general formula but containing no water-solubilizing group generally have a markedly less stabilizing action more particularly a marked desensitizing effect.

The compounds having the structures listed below are representative of those falling within the scope of the abo /e general formula.

The above specific compounds can be illustrated by the following preparations: Preparation 1 Compound 1 2-(Z-imidazolyl)-5-sulphoimidazole was prepared by sulphonation of 2,2-diimidazole according to J .prakt. C e 4.. .2o-

Preparation 2 Compound 2 60 g (0.307 mole) of 2-(3-pyridyl)benzimidazole were added with stirring to 150 ccs (2.3 moles) of chlorosulphonic acid and the mixture was stirred for 8 hours. The reaction rnixturewas pouredinto 1 kg' of ice-water. The 2-(3-pyridyl)'5(6)- chlorosulphonylbenzimidazole formed separated in the prepared as form of an oil. The sulphochloride was hydrolyzed by boiling and the crystalline product formed upon cooling in ince was recrystallized from water. Yield 22 g of 2-(3-pyridyl)-5(6)-sulphobenzimidazole.% hydrate.

Preparation 3 Compound 3 A mixture of 18 g (0.08 mole) of 2-carboxy-5- sulphopyridine and 8.64 g (0.08 mole) of ophenylenediamine was heated for 6 hours at 160C in 25 g of polyphosphoric acid. After having been cooled the mixture was poured into200 ccs of ice-water and the'precipitate formed was filtered by suction and redissolved in 100 ccs of 1N sodium hydroxide. The solution was acidified by means of hydrochloric acid whereby 13 g of 2-(5(6)-sulpho-2-pyridyl) benzimidazole precipitated.

Preparation 5 Compound 5 12.3 g (0.1 mole) of isonicotinic acid and 18.8 g (0.1 mole) of 3;4-diaminobenzenesulphonic acid were heated for 6 hours at 200C in 50 g of polyphosphoric acid. After having been cooled the reaction mixture was poured into 300 ccs of water whereupon the precipitate formed was filtered by suction and recrystallized from water. Yield 22 g of 2-(4-pyridyl)-5(6)- sulphobenzimidazole. phosphoric acid.

19 g of 2-(2-pyridyl)-5(6)- 6 Preparation 6 Compound 6 227 g (1.16 mole) of 2-(4-pyridyl)benzimidazole were added with stirring to 567 ccs (8.7 mole) of chlorosulphonic acid whereupon the mixture was refluxed for 8 hours. The reaction mixture was poured into 4 kg of ice-water. The 2-(4-pyridyl)-5(6)- chlorosulphonylbenzimidazole separated in the form of a brown oil.

The sulphochloride was hydrolyzed by boiling and the pH of the solution obtained was adjusted to pH 2 by means of sodium carbonate. The reaction mixture was kept overnight at 0C and the crystallized product was filtered by suction and then recrystallized from water. Yield 207 g of 2-(4-pyridyl)-5(6)- sulphobenzimidazolemonohydrate.

Preparation 7 Compound 7 a. A solution of 18.8 g (0.1 mole) of 3,4-diaminobenzenesulphonic acid and 5.9 g (0.05 mole) of succinic acid in 150 ccs of 6N hydrochloric acid was refluxed for 12 hours. The mixture was concentrated by evaporation and the residue was washed with 250 ccs of water. Yield: 16 g of 1,2-bis-5(6)-sulpho-2- benzimidazolyl)-ethane.

b. This compound can also be prepared as described in Swiss Patent Specification 235,570 by sulphonation of 1,2-bis-2-(benzimidazolyl)-ethane with fuming sulph d.-

Preparation 9 Compound 9 To a solution of 18 g (0.06 mole) of 1,4-bis(2- benzimidazolyD-butane in 180 ccs of sulphuric acid were added dropwise 54 g of fuming sulphuric acid (24 percent of S0 The reaction mixture was kept between and C until a sample taken dissolved completely in a solution of sodium carbonate. The reaction mixture was poured into ice-water and the precipitate formed was filtered by suction. The white pow der formed was purified by dissolving it in sodium carbonate and then precipitating it by means of acetic acid. Yield 19 g of 1,4-bis(5(6)-sulpho-2- b enzimidazolyhbutane.

Preparation 11 Compound 11 12.3 g of picolinic acid and 23.4 g of 3-amino-4- ethylaminobenzenesulphonic acid were heated for 6 hours at 200C in 50 g of polyphosphoric acid. After having been cooled the reaction mixture was poured into 300 cos of water, the precipitate formed was filtered by suction and recrystallized from water. Yield v 6 g of 1-ethyl-2-(2-pyridyl)-5(6 )-sulphobenzimidazole.

14.9 (0.1 mole) of 2-(2-pyridyl)acrylic acid and 18.8 g (0.1 mole) of 3,4-diaminobenzenesulphonic acid were heated for 6 hours at 200C in 50 g of polyphosphoric acid. After having been cooled the reaction mixture was poured into 300 ccs of water and the precipitate formed was recrystallized from 300 ccs of 1N hydrochloric acid. Yield 24.5 g of 2-[B-(2-pyridyl)- vinyl]-(6)-sulphobenzimidazole hydrochloride monohydrate.

Preparation 13 2 Compound l3 g (0.036 mole) of 2-(5-sulpho-2- pyridyl)benzimidazole were added with stirring to 41.5 g (0.27 mole) of chlorosulphonic acid and the mixture was refluxed for 8 hours. The reaction mixture was poured into 150 g of ice-water and the solution was refluxed for 1 hour. By addition of a saturated solution of barium hydroxide, barium sulphate was precipitated. The barium sulphate was filtered by suction and washed with water. The filtrates were conducted over beads of insoluble-sulphonated polystyrene as cation exchanger. The eluate is evaporated till dry and the residue was recrystallized from ethanol. Yield 1 2 g of 2- (5-sulpho-2-pyridyl)-5(6)-sulphobenzimidazole dihydrate.

Preparation 14 Compound 14 23.8 g of 3,4-diaminonaphthalenesulphonic acid and 12.3 g of 2-pyridinecarboxylic acid werd dissolved in 100 g of polyphosphoric acid and heated for 6 hours at 200C. After having been cooled the reaction mixture was poured into water and the precipitate formed was filtered by suction. The precipitate was redissolved in alkali and precipitated again by acidification whereupon it was recrystallized from water. Yield 17 g of 2-(2-pyridyl )-7-sulphol H-naphtho[ 1 ,2-d]imidazole. Preparation Compound 15 17 g of N ,N-bis[ 2-benzimidazolyl methyl]methylamine were dissolved in 109 g of chlorosulphonic acid. The mixture was refluxed for 15 hours and poured into ice-water. The precipitate formed was filtered by suction, redissolved in alkali, filtered over decolourizing carbon and acidified. Yield 15 g of N,N- bis(5(6)-sulpho-2-benzimidazolylmethyl)- methylamine.

Preparation 16 Compound 16 18.8 g of 3,4-diaminobenzenesulphonic acid and 17.3 g of Z-quinolinecarboxylic acid were dissolved in 50 g of polyphosphoric acid and heated for 6 hours at 200C. After having been cooled the reaction mixture was poured into water, the precipitate formed was filtered by suction and redissolved in alkali. The product was precipitated by acidification and the precipitate was recrystallized from water. Yield 15 g of 2-(2- quinolyl)-5(6)-sulphobenzimidazole.

Preparation 17 Compound 17 A mixture of 2-(2-benzimidazolyl)-3H-imidazo[4,5- b] pyridine prepared as described in J.Chem.Soc. 33 (1967) and 25 ccs of chlorosulphonic acid was heated for 8 hours on a steam bath whereupon the reaction mixture was poured into ice-water. The sulphonyl chloride formed was refluxed for 8 hours in 100 ccs of concentrated hydrochloric acid. The precipitate formed upon cooling was filtered by suction. Yield 5 g of 2-(5(6)-sulpho-2-benzimidazolyl)-3H- imidazo[4,5-b]pyridine.

sodium salt.

Preparation 18 Compound 18 A mixture of 11 g of 2-(4-thiazolylmethyl)- benzimidazole prepared as described in BulLSoc. Chim.France 1966, 1545 and 25 ccs of chlorosulphonic acid was heated for 8 hours on a steam bath whereupon it was poured into ice-water. The sulphonyl chloride formed was refluxed for 8 hours in ccs of concentrated hydrochloric acid. The precipitate formed upon cooling was filtered by suction. Yield 6 g of 2-(4-thiazolylmethyl)-5(6)-sulphobenzimidazole. Preparation 19 Compound 19 3-sulpho-5-(4-pyridyl)-l H- 1 ,2,4-triazole was pared as described in J.Chem.Soc. 1967), 661. Preparation 20 Compound 20 2-(2-A -imidazolinyl)-5(6)-sulphobenzimidazole was prepared as described in J.Chen 1.Soc. (1967) 33. Preparation 21 Compound 21 To a solution of 11.4 g of 1,2-bis-(5-mercapto-l1-1- 1,2,4-triazole-3-yl)ethane prepared as described in Bull. Soc.Chim.Belg. 75, 358 (1966) and 12 g of sodium methylate in ccs of methanol 18 g of propanesultone were added. The mixture was refluxed for 3 hours and then filtered over decolourizing carbon. The filtrate was concentrated by evaporation and the residue was dissolved in ethanol. The product was precipitated by means of acetone. Yield 22 g of 1,2-bis[5- (3-sulphopropylthio)-11-1-1,2,4-triazol-3-yl]-ethane dipre- Preparation 22 TNT To a solution of 11.4 g of 1,2-bis(5-mercapto-1H- 1,2,4-triazol-3-yl)-ethane and 12 g of sodium methylate' in 150 ccs of methanol, 20 g of 1,1,3-trimethylpropanesultone were added. The mixture was refluxed for 3 hours and filtered over decolourizing carbon. The filmm is 9 4 99bXQYPBQQliQD21 93 1 re d dissolved in ethanol. The product was precipitated by means of acetone. Yield 30 g of 1,2-bis[5-(1,3- dimethyl-3-sulpho-butylthio)-1H-l ,2,4-triazol-3-yl1- ethane disodium salt. 7 i Wm Preparation 23 Compound 23 44 g of 3-phenyl-5-(2-pyridyl)-pyrazole prepared as described in .l.prakt.Chem., Vol. 34 (1966) 64, and 1 16 g of chlorosulphonic acid were refluxed for 8 hours. The reaction mixture was poured into water and the precipitate filtered by suction. It was redissolved in water and the solution formed was refluxed for 1 hour. The solution was concentrated by evaporation and the residue formed recrystallized from aqueous isopropanol. Yield 9 g of 3-(m-sulphophenyl)-5-(2-pyridyl)- pyrazole i V W H 7 W 7 Preparation 24 Compound 24 27.4 g of the disodium salt of 2-mercapto-5(6)- sulphobenzimidazole and 17 g of 2- chloromethylbenzimidazole were suspended in 250 ccs of dimethyl formamide and heated with stirring for 6 hours at 70C. The reaction mixture was evaporated till dry, and the residue was taken up in alkali. The solution was filtered over decolourizing carbon and acidified. The precipitate formed was recrystallized from water. Yield 7 g of 2-(2-benzimidazolylthio)-5(6)- sulphobenzimidazole. Preparation 25 Compound 25 To a solution of 7.5 g of 5-(4-pyridyl)-1H,1,2,4- triazole-3-thiol prepared as described in Rec.Trav.- Chim. Pays-Bas 73 (1954) 113, and 2.27 g of sodium methylate in 250 ccs of methanol, 5.12 g of propanesultone werde added. The mixture was refluxed for 4 hours and evaporated till dry. The residue was dissolved in water, filtered and acidified. The precipitate formed was recrystallized from water. Yield 5.5 g of 3-(3-sulphopropylthio)-5-(4-pyridyl)-1i-l-l ,2,4- triazole. Preparation 26 Compound 26 l,2-bis-(Z-benzimidazolyl)-ethanesulphonic acid sodium salt was prepared as described in United States P t p ifisat qaNe. 3.29.52.85.21.-.

Preparation 27 Compound 27 To a suspension of 37.8 g of the sodium salt of 2- mercapto-S-sulphobenzimidazole in 100 ml of water, a solution of 12 g of sodium hydroxide in 60 ml of water was added with stirring so that the benzimidazole compound dissolved completely.

At room temperature, a solution of 17.75 g of chloromethyltetrazole in 100 ml of water was added dropwise in minutes. The mixture was heated for 2 hours at 75C and then cooled. The solution obtained was diluted with water to make 2 litres and then passed over an ion-exchanger. The solution was concentrated by evaporation, the residue recrystallized from 1 litre of dimethylformamide, filtered off, washed with ethanol and ether and dried at 100C in vacuum. en;

Preparation 28 Compound 28 27.4 g of the disodium salt of 2-mercapto-5(6)- sulphobenzimidazole and 12.8 g of 2- chloromethylpyridine were suspended in 200 ccs of dimethylformamide and heated for 6 hours with stirring at 80C. The sodium chloride formed was filtered off by suction, whereupon the solution was evaporated till dryness. The residue was dissolved in water and aciditied with acetic acid. Yield 11 g of 2-( 2- nx y met!!!l hi bl la nhohea m@5015-. Preparation 29 Compound 29 To a solution of 18 g of 1,3-bis-(5-mercapto-1H- l,2,4-triazol-3-yl)-propane and 8 g of sodium methylate in 200 ccs of methanol, a solution of 18 g of propane-sultone in 300 ccs of methanol was added. The mixture was refluxed for 4 hours and evaporated till dryness. The residue was dissolved in water and conducted over an ion exchanger. The eluate is once again evaporated till dryness and the residue is recrystallized from water. Yield 10 g. Preparation 30 Compound 30 To a solution of 18 g of l,3-bis(5-mercapto-1H- l,2,4-triazol-3-yl)-propane in 300 ccs of water an aqueous potassium permanganate solution wasadded dropwise until the colour did not disappear any more. The solution was filtered, conducted over an ion exchanger and evaporated. The residue was recrystallized from w ter: s e ,9 s-

Preparation 31 Compound 31 27.4 g of the disodium salt of 2-mercapto-5(6)- sulpho-benzimidazole and 8.7 g of dibromomethane were suspended in 200 ccs of dimethylformamide and heated with stirring for 3 hours at 100C. The solution was filtered and concentrated by evaporation. The residue was washed with methanol and recrystallized from a mixture of ethanol and water. Yield 8 g.

The antifoggants according to the present invention. are generally incorporated into the silver halide emulsion layer of the light-sensitive material. The way in which the compounds of use according to the invention are added to emulsions is not critical and the addition can be made during any the emulsion preparation; they can be added before or after the emulsion has been optically sensitized, preferably just before coating of the emulsion on a suitable support such as for example paper, glass or film.

Instead of incorporating the compounds of the invention into the emulsion layer they can also be incorporated into another layer of the photographic material,

e.g. a gelatin antistress layer or intermediate layer, which is in water-permeable relationship with the said emulsion layer or into one of the processing baths for said photographic material.

The antifoggants of use according to the present invention may be incorporated into any type of lightsensitive material comprising a silver halide emulsion layer e.g. a spectrally sensitized or non-sensitized silver halide emulsion layer, a silver halide emulsion layer of use in diffusion transfer processes for the production of silver images, an X-ray emulsion layer, and an emulsion layer sensitive to infra-red radiation. They may be incorporated into high speed negative materials as well as into rather low speed positive materials. Various silver salts may be used as the light-sensitive salt e.g. silver bromide, silver iodide, silver chloride, or mixed silver ha s-sly tshlq qbzomi e or Silver zwmqiosi q- The silver halides are dispersed in the common hydrophilic colloids such as gelatin, casein, zein, polyvinyl alcohol, carboxymethylcellulose, alginic acid, etc., gelatin being, however, favoured.

The amount of antifoggant employed in the lightsensitive silver halide material depends on the particular type of emulsion and the desired effect and can vary within very wide limits. The optimum amount of antifoggant to be added is best determined for each particlular type of emulsion by trial. Generally, the most suitable concentration is between 0.2 millimole and 30 millimoles of antifoggant per mole of silver halide.

The light-sensitive emulsions may be chemically as well as optically sensitized. They may be chemically sensitized by effecting the ripening in the presence of small amounts of sulphur containing compounds such as allyl thiocyanate, allyl thiourea, sodium thiosulphate, etc. The emulsions may also be sensitized by means of reductors for instance tin compounds as described in our United Kingdom Patent specification No. 789,823 andsmall amounts of noble metal compounds such as gold, platinum, palladium, iridium, ru- IPQ l E QI IQdlHHLW. mama-..

Other addenda such as hardening agents, wetting agents, plasticizers, colour couplers, developing agents and optical sensitizers can be incorporated into the emulsiqn in t he usual way.

. The antifoggants according to the present invention are particularly suitable foruse in conjunction with compounds which sensitize the emulsion by development acceleration for example alkylene oxide polymers. These alkylene oxide polymers may be of various with the antifoggants of use according to the invention are the onium derivatives of amino-N-oxides as described in Belgian Patent specification No. 686,520.

The stabilizers according to the invention can also be used in conjunction with other known stabilizers for in stance with heterocyclic nitrogen containing thioxo compounds such as benzothiazoline-2-thione and lphenyl-A2-tetrazoline-5-thione, with mercury compounds such as those described in Belgian Patent Speciflcations 524,121, 677,337, 707,386 and 709,195 and as mentioned above, preferably with compounds of the hydroxytriazolopyrimidine type (hydroxyazaindoli- 5 als formed were determined shortly after preparation and after incubation for 5 days at 57C and 34 percent relative humidity. The values obtained are listed in the table below.

Development occurred at 20C for 5 min. in u developing solution having the following composition:

water 800 ccs p-monomethylaminophenol sulphate 1.5 g sodium sulphite (anhydrous) 50 g hydroquinone 6 g zines), particularly in extreme storage and developifixg fi ggfis ment circumstances. ,water to make 7, 7,. ,W, 100.0 ccs.

Table Fresh material incubated material Speed Speed Compound added Fog Gradation 1 W 11 F g Gradation 1 l1 none 0.o9 10? 100 100 0.71 1.62 95 as compound 22 0.09 1.95 100 93 0.29 1.81 129 110 compound 23 0.06 2.04 89 89 0.19 1.80 151 112 EXAMPLE 2 The following examples illustrate the stabilizing and fog-inhibiting action of the compounds corresponding to the above general formula. In these examples, the values 1 and Il given for the speed are relative values corresponding with density 0.1 above fog and density Example 1 was repeated with the difference that the emulsion was divided into four aliquot portions to which the compounds listed in the table below were added in the concentration given. The sensitometric re- 1 above fog respectively; the values of 100 are given to sults obtained ar e li stedin the following table.

Compound added per kg of emulsion F 'gsh material lngubatgd material none 1 millimole of com ound l1 2 mi limoles of compound 12 l millimole of 1-ethyl-2-(2- pyridyl)-benzimidazole fog gradaweed fog gradation 1 11 tion 1 11 the emulsions comprising no stabilizer of the invention.

EXAMPLE 1 A conventional photographic gelatino silver bromo- 55 iodide emulsion (4.5 mole iodide) comprising per kg an amount of silver halide equivalent to 50 g of silver nitrate was divided into three portions. To two of these emulsion portions was added a compound as listed in As can be seen from these results, compounds similar 50 to those of the invention but containing no watersolubilizing group reduce the fogging tendency but at the cost of a considerable reduction of the sensitivity. EXAMPLE 3 Example 1 was repeated with the difference that the emulsion was divided into four aliquot portions to which the compounds listed in the table below were added in the concentration given.

T h e following sensitometric results were attained.

compound 3 EXAMPLE 4 Example 1 was repeated with the difference that the emulsion was divided into seven aliquot portions to which the compounds listed in the table below were added in a concentration of 1 millimole per kg of emul- S1011.

Th ifq lvn aassasitemstt s. a t)ysrsa tansd-.

This emulsion was divided into two aliquot portions A and B and to one of them (B) was added 500 mg of p vn 8 Writs 9 emu on The emulsion portions were both applied to cellulose triacetate supports and dried.

The materials A and B obtained were both exposed M in thesameeircumstances through a grey wedge and Compound added V Fresh material per kg of fog gradaspeed fog gradaspeed emulsion tion 1 11 tlon I 11 none 0.36 1.74 100 100 1.08 1.40 78 65 compound 7 0.12 2.14 89 105 0.31 1.71 107 100 compound 8 0.16 1.40 81 69 0.42 1.36 85 69 compound 4 0.13 1.75 67 74 0.38 1.66 85 83 compound 0.12 2.22 67 76 0.17 2.16 71 79 compound 10 0.10 2.12 42 51 0.10 1.96 50 57 2,6-bis(2- benzimidazolyl)- pyridine From the results it appears that compounds similar to 20 developed min. at 20C in a developer having the fallvwias sompositiom water 750 ccs N-methyl-p-aminophenyl sulphate 2g anhydrous sodium sulphite 100g hydroquinone 5 g granular borax 2 water to make 100 ccs The fog produced in the freshly prepared materials and identical materials that'have been stored for 10 days at 57C and 34 percent relative humidity is listed in the following table. The gradation and speed of the fresh materials andincubated materials have remained the same.

A washed negative gelatin silver bromoiodide emulsion (average grain size of the silver halide 0.8 pt) the silver halide of which consists of 94.5 mole percent of silver bromide and 5.5 mole percent of silver iodide, was ripened at C. The emulsion ready for coating contained per kg g of silver halide, 75 g of gelatin, 30 mg of optical sensitizer corresponding to the follownsstrustu a t9 pound JmL-mmht. w

added fog grada- P fog gradage g d tion. 1 11 tion 1 11 none 7 0.09 1.67 100 0.65 1.14 144 93 compound 24 0.08 1.62 81 87 0.29 1.36 138 117 EXAMPLE 6 4O Fog produced in 7 Example 5 was repeated but now compound 9 was Material Fresh materials lncubated materials used instead of compound 24. Material A ,14 The following sensitometric results were 2111311161 Maleflal B 0J3 Compound lncubated material added fog gradagpggd fog gradaspggd tion 1 11 tion 1 11 none 0.13 1.90 I00 100 1.31 1.50 65 61 compound 9 0.09 2.03 91 85 0.38 1.75 69 85 EXAMPLE 7 EXAMPLE 8 A silver bromoiodide emulsion as described in example 7 was prepared and divided into two aliquot portions A and B. To one of these (B) were added 30 mg of compound 10 per kg of emulsion.

The emulsions were both applied to cellulose triacetate supports and dried.

5-methyl-7-hydroxy-s-triazolo[1,5-

15 16 that produced in the material comprising a compound thimidazole nucleus, an imidazopyridine nucleus, according to the invention in addition to the said an imidazole nucleus, a pyrazole nucleus, a triazole triazolopyrimidine namely 0.11. nucleus or a tetrazole nucleus, 7 W The gradation and the speed remamed practically un- A stands for a Single chemical bond an aikylene changed' group contalnmg from one to four carbon atoms 1n EXAMPLE 9 a carbon to carbon chain, including alkylene interrupted by oxygen or a -N( R) group, wherein R stands for hydrogen or a one to four carbon atom alkyl group, arylene, alkenylene and -S-alkylene-S- or -S-alkylene, the alkylene groups of which will contain from one to four carbon atoms in a carbon to carbon chain and can be interrupted by oxygen or an -N(R)- group wherein R stands for hydrogen and a one to four carbon atom alkyl group.

A conventional photographic gelatino silver bromoiodide emulsion (4.5 mole percent iodide) comprising per kg an amount of silver halide equivalent to 50 g of 10 silver nitrate was divided into 4 portions. To 3 of these portions was added a compound as listed in the table below in the concentration given. The emulsions were coated on a conventional support and dried.

The values of speed, gradation and fog of the materials formed were determined shortly after preparation X Stands f r a 5- or 6- membered heterocycle, said and after incubation for 5 days at 57C and 34 percent heterocycle comprising the grouping =N. relative humidity. The values obtained are listed in the d herem a carboxyl group or sulpho group 1n acid t bl b l or salt form is hnked directly or indirectly to the group- Exposure occurred through a step-wedge with coni g Z a /0 X /0 Said bidentate reagent being stant 0.15. present in a fog-inhibiting amount.

Development occurred at 20C for 5 min. in a devel- 2. Photographic material according to claim 1, oper solution having a composition as given in Example wherein X stands for an imidazole nucleus, a benzimidl. V V a, i d W W 7 W i T 7 V 7 azole nucleus, a naphthimidazole nucleus, an

Compound added Fresh matgrial lncubated material per kg of fog gradaspggg fog gradaspeed emulsion tion 1 ll tion I ll none 0.13 1.73 100 100 0.66 1.28 204 83 150 mg of(l) 0.13 1.73 107 78 0.25 1.42 195 135 l millimole of compound 29 0.12 1.85 129 102 0.43 1.63 200 135 2 millimoles of compound 29 0.11 1.83 115 93 0.22 1.62 200 141 (i g i .g-n b -iny mgnnfi gi V i imidazopyridine nucleus, an imidazoline nucleus, a pyr- We cl im; azole nucleus, a pyridine nucleus, a quinoline nucleus, 1, Photographic material comprising a support and at a thiazole IlUClCUS, a triazole nucleus or a tetrazole nuleast one light-sensitive silver halide emulsion layer Cleuscomp ising i id l i layer d/ i at least one 3. Photographic light-sensitive silver halide material t bl layer coated at h Same id f the according to claim 1, wherein said heterocyclic bidenrt as th id l i layer t l t one h tate reagent for silver is present in the light-sensitive silcyclic bidentate reagent for silver corresponding to the halide emulsion layer in an amount betwfien f ll i l il l H v W and 30 millimoles per mole of silver halide.

w 4. Photographic light-sensitive silver halide material according to claim 1, wherein said material also comprises a hydroxytriazolopyrimidine stabilizer.

I 5. Photographic light-sensitive silver halide material l according to claim 1, wherein said material also comwherein prises a polyoxyalkylene development accelerator.

R stands for hydrogen or a One to f r Carbon atom 6. Photographic light-sensitive silver halide material alkyl group, according to claim 1, wherein said emulsion layer is a Z represents the atoms necessary to complete an imgelatino silver halide emulsion layer idazole nucleus, a benzimidazole nucle 1 nap -..Lj in... 

2. Photographic material according to claim 1, wherein X stands for an imidazole nucleus, a benzimidazole nucleus, a naphthimidazole nucleus, an imidazopyridine nucleus, an imidazoline nucleus, a pyrazole nucleus, a pyridine nucleus, a quinoline nucleus, a thiazole nucleus, a triazole nucleus or a tetrazole nucleus.
 3. Photographic light-sensitive silver halide material according to claim 1, wherein said heterocyclic bidentate reagent for silver is present in the light-sensitive silver halide emulsion layer in an amount between 0.2 and 30 millimoles per mole of silver halide.
 4. Photographic light-sensitive silver halide material according to claim 1, wherein said material also comprises a hydroxytriazolopyrimidine stabilizer.
 5. Photographic light-sensitive silver halide material according to claim 1, wherein said material also comprises a polyoxyalkylene development accelerator.
 6. Photographic light-sensitive silver halide material according to claim 1, wherein said emulsion layer is a gelatino silver halide emulsion layer. 